Oil circuit breaker for high interruption currents



w. PUCHER 3,010,003

R FOR HIGH INTERRUPTION CURRENTS Nov. 21, 1961 OIL. CIRCUIT BREAKE Filed Oct. 15, 1959 INVENTOR. h/alzer Emile)" 8/ flffomef.

thee

OIL CIRCUIT BREAKER FOR HIGH INTER- RUPTION CURRENTS Walter Pucher, Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Oct. 15, 1959, Ser. No. 846,671 Claims priority, application Sweden Oct. 23, 1958 4 Claims. (Cl. 200-150) In extinguishing chambers for oil circuit breakers it is already known to let the arc gases generated at an interruption during the first part of a breaking action increase the gas pressure in a closed annular space arranged above the oil surface in the extinguishing chamber. At a predetermined distance between the contacts of the circuit breaker, one or a plurality of outlet openings for the oil, below the annular space, is uncovered by the movable contact of the circuit breaker, so that the oil is forced by the gas pressure in this space out through the open ings against the arc. This means that the arc must always be drawn out to some length before the extinguishing flow of oil begins. At high interruption current it is, however, important that the extinguishing flow of oil begin as soon as the value of the current passes through zero. This is not always the case in the above mentioned constructions.

The present invention concerns an oil circuit breaker comprising an extinguishing chamber immersed in oil, which chamber at the top is closed by a cover. inside the extinguishing chamber a cylinder, projecting downwardly from the cover, carries the stationary contact, so that the extinguishing chamber, the cylinder and cover at the upper part of the extinguishing chamber form an annular closed space which, through one or a pluraiity of oil level openings arranged in the wall of the extinguishing chamber, communicates with the oil outside the extinguishing chamber. The movable pin-shaped contact can be passed through an opening in the bottom of the extinguishing chamber to the stationary contact. The in vention is characterised in that the stationary contact is shaped like a nozzle, which is uncovered when the contacts are separated, at which time the interior of the extinguishing chamber through an outlet channel through the cylinder, communicates with the space outside the extinguishing chamber.

By the invention an extinguishing chamber is obtained in which a heavy flow of oil begins along the arc and out through the nozzle of the stationary contact at about the same time as the magnitude of the current passes through zero for the first time. The extinguishing chamer according to the invention also has the advantage that the arc is not drawn out through a wall of isolating material before the extinguishing of the arc begins.

Although the nozzle in the stationary contact is already uncovered when the contacts separate, the pressure in the extinguishing chamber, however, at interruption of lower currents will not be sufficiently high for the extinguishing to be effective. Because of this a stop valve is inserted in the outlet channel from the nozzle, which stop valve is not opened until a predetermined over pressure has been reached inside the extinguishing chamber. In order to make the interruption of, lower currents still more certain and to prevent the are being drawn out of the extinguishing chamber, one or a plurality of oil pockets has been arranged in the lower part of the chamber, through which pockets the movable contact is passed.

On. the other hand, to decrease the pressure strain on the extinguishing chamber at interruption of large currents, the extinguishing chamber, besides oil level openings, the openingfor the movable contact and the nozzle of the stationary contact, is also provided with extra out- Patented Nov. 21, 1961 let openings, through which the interior of the extinguishing chamber communicates with the space outside the extinguishing chamber.

The accompanying figure shows a longitudinal section of an extinguishing chamber according to the invention. From the figure it is evident that the extinguishing chamher is constructed for circuit breakers with downwardly directed contact movement during a breaking action.

In the figure, .1 designates an extinguishing chamber, which is provided with a cover 2. In the cover a cylinder 3 is fastened, which carries the stationary nozzleshaped contact 4. A movable pin-shaped contact 5 can be passed through openings 6 in to the stationary contact 4. Part of the extinguishing chamber 1 is immersed in oil and its interior communicates with the surrounding oil through the oil level openings 7, the pressure equalizing openings 8 and at open circuit breaker also through the openings 6. When the contacts are separated, the in terior of the extinguishing chamber 1 furthermore com municates with the space above the oil, which surrounds the extinguishing chamber 1, through the stationary nozzle-shaped contact 4 through an outlet channel 9. In this a spring-loaded stop valve 10 is arranged, which is opened at a predetermined overpressure in the extinguishing chamber. The stop valve 10 is provided with a channel 11. The extinguishing chamber 1, the cylinder 3 and the coverZ form in the upper part of the extinguishing chamber an annular closed space 12. The extinguishing chamber 1 is in its lower part provided with one or a plurality of oil pockets 13.

The circuit breaker operates in the following way. When the movable contact 5 at a breaking action leaves the stationary nozzle-shaped contact 4, an arc is drawn whichgenerates gas which forms a bubble around the point of interruption. This bubble forces aside the surrounding oil with the result that the oil level below the annular space 12 rises and the gases in this space are compressed. I

When the value of the interruption current approaches zero, the pressure in the gas bubble around the are decreases and the oil in the extinguishing chamber 1 is forced by the gas pressure in the annular space 12 against the arc and out through the stationary nozzle-shaped contact 4, so that the arc is extinguished. In the open position of the circuit breaker, the extinguishing chamber is again filled with oil which flows in through the openings 6 and 8. To ensure that the oil below the annular space 12 and in the outlet channel 9 after a :breaking action will always rise to the same level, the extinguishing chamber is provided with the oil level openings 7 and the stop valve 10 with the channel 11. Without these. the extinguishing chamber 1 and the outlet channel 9 might, after repeated breaking actions, be gradually filled with breaking gases.

During an interruption of low current, the pressure in the extinguishing chamber at first is so low that the stop valve 10 is closed. Because of this, the pressure in the annular space 12 is increased more rapidly and especially to a sufficiently high value for an effective extinguishing of the arc. When this value has been reached, the gases in the annular space 12 exert such a pressure on the oil in the extinguishing chamber 1, that the stop valve 10 is opened and the extinguishing flow of oil out through the stationary nozzle-shaped contact 4 begins. To make theextinguishing of the arc still'more certain, the movable contact is drawn through one or a plurality of oil pockets 1?: in the bottom of the extinguishing chamber.

During interruption of high currents, on the other hand, such a high pressure may occur in the extinguishing chamberthat it might be in danger of exploding. To prevent this, pressure equalizing openings 3 are arranged in the lower part of the extinguishing chamber. 7

The extinguishing chamber is shown in FIGURE 1 only partly immersed in oil but will of course function also when it is fully immersed in oil. In the last case, however, the pressure strains on the extinguishing chamber will be greater due to the larger amount of oil, which the escaping breaking gases must force aside. The increased pressure strains are, however, balanced by the fact that the escaping hot breaking gas is not able to damage the isolation, which is now protected by oil.

I claim:

1. Oil circuit breaker comprising an extinguishing charnber immersed in oil, which chamber at the top is closed by a cover, inside said chamber a cylinder projecting downwardly from the cover and carrying the stationary contact, so that said chamber, cylinder and cover above the oil surface in said chamber form an annular closed space and that said chamber, through one or a plurality of oil level openings arranged in the Wall of the extinguished chamber, communicates with the oil outside the extinguishing chamber, and a movable pin-shaped contact which, through an opening in the bottom of the extinguishing chamber, can be passed in to the stationary contact, characterized in that the stationary contact is shaped like a nozzle which is uncovered when the contacts separate so that the interior of the chamber via said nozzle, and an outlet channel through the cylinder communicates with the space outside the extinguishing chamher.

2. Oil circuit breaker according to claim 1, characterised in that a stop valve is arranged in the outlet channel which stop valve is opened responsive to a predetermined over pressure in the extinguishing chamber.

3. 'Oil circuit breaker according to claim 1, characterised in that in the lower part of the extinguishing chamber one or a plurality of oil pockets has been arranged through which the movable contact is passed.

4. Oil circuit breaker according to claim 1, characterised in that the interior of the extinguishing chamber communicates with the space outside the extinguishing chamber, besides through the oil extinguishing channels, the opening for the movable contact and the stationary nozzle-shaped contact, also through the pressure equalizing openings.

References Cited in the file of this patent UNITED STATES PATENTS 2,022,241 Kopeliowitsch u- Nov. 26, 1935 FOREIGN PATENTS 683,017 Germany October 27, 1939 695,436 Germany Aug. 24, 1940 

